Posts Tagged ‘1928 – 31 Model A Ford chassis considerations’

One of my main goals in the design for the 1928 to 31 Model A Ford Street Rod chassis / frame was to incorporate as many of the 1986 C4 Corvette suspension components as possible. Initially, I even wanted to use the front mono composite spring from the Corvette. This spring is huge and at the time did not seem like a practical idea. Having acquired a variety of automotive parts over a short period of time, I had sitting in the shop, 4 Jaguar coil over shocks. The distance between the mounting holes was prefect for my application. These shocks came from the rear end of a mid 1980’s full size Jaguar Sovereign 4 door car. The Jaguar Sovereign is a heavy car, and my 1929 Ford Roadster hot rod would be much lighter. I thought there might be a possibility to use the coil over shocks on my hot rod. Temporary mounting brackets were made for the shocks. The motor and transmission were temporarily mounted into the hot rod chassis / frame. I even added several bags of sand for added weight. The shocks were mounted to the front of the new 1928 to 31 Model A Ford Street Rod chassis / frame. I measured the ground clearance for a reference point then stood on the chassis and started bouncing my 6’-4”, 250 pound body up and down on the chassis as hard as I could. Very little movement was observed. It was then I realized that I could save a bit of money for the time being and use the Jaguar coil over shocks in the front of my 1929 Ford Roadster. Later on, once the car is on the road, I do intend to replace these shocks with nice and shiny chrome coil over shocks.

C4 Corvette upper control arm mount for a 1928 - 1931 Ford Model A Hot Rod - the upper control arm mount is tack welded in place and the lower right angle cross member gussets have be installed.

Everything is starting to come together nicely with the front 1986 C4 Corvette suspension for the 1928 to 31 Model A Ford Street Rod chassis / frame. The front suspension mock up produced favourable results with the desired ride height. Not only that, all of suspension components taken from the1986 C4 Corvette look great on the new hot rod frame. Now it came time to create a proper chassis cross member, and the required mounting brackets for the front suspension.

C4 Corvette upper control arm mount for a 1928 - 1931 Ford Model A Hot Rod - inside view - the shocks are mounted and tested to determine if the spring rate is adequate.

For the cross member I used 2” x 4” x 0.1” rectangular tubing, heavy wall 1.25” round tubing for the lower control arm mounts, and 0.25” plate steel for the upper control arm mounts. Inside the 1.25” heavy wall round tubing, bronze bushings were pressed into each end providing an inner diameter of 0.5” for the lower control arm mounts. Originally the lower control arms were fastened to the 1986 C4 Corvette cross member with metric bolts about 3” long for each pivot point on the lower control arms. I did notice a minor amount of wear on the original C4 Corvette cross member mount holes for the lower control arms. The design for my hot rod will allow for sealed lubrication in the lower control arm cross member round tubes eliminating wear problems. The only thing left to do, is enlarge the inside bushing diameter of the C4 Corvette lower control arms. This was accomplished very carefully, using a 0.5” cobalt drill bit. High speed drill bits will not work for this task.

Wanting a strong chassis / frame, one that will not flex when picked up by one corner of the chassis, I welded in right angle gussets from the lower front cross member to the inside of the frame rails. Scraps of 2” x 4” rectangular tubing was used for this job. Now this created a minor problem for the stock 1986 C4 Corvette steering rack. The steering rack and the intermediate steering shaft needed a bit of clearance space notched out of the right angle gussets I just welded into the cross member / chassis. To solve the problem, a very small section of round exhaust tubing was moulded into the gusset. This took a few hours to do and make it look nice.

C4 Corvette upper control arm mount for a 1928 - 1931 Ford Model A Hot Rod - inside view showing the gussets for the upper control arm brackets. Now a bit of grinding is in order to make everything smooth.

Work on the upper control arm brackets started. Using the plasma cutter, and a wooden template, I cut out 2 identical brackets. The plasma cutter produces a very clean cut, so it didn’t take too long finishing the edges of these brackets. The highest part of these brackets would stand a little more than 4” from the top of the frame rail. Again, wanting everything very strong, I fabricated gussets to strengthen the upper control arm brackets to the frame / chassis.

C4 Corvette upper control arm mount for a 1928 - 1931 Ford Model A Hot Rod - inside view showing the exhaust tubing massaged into the cross member. This is required to have the proper clearance for the 1986 C4 steering rack and intermediate shaft.

Now it was time to weld everything in place.

C4 Corvette upper control arm mount for a 1928 - 1931 Ford Model A Hot Rod - outside view showing my first version of the upper mount for the coil over shock. I didn't like the way this looked and ended up removing it.

Come back next week to see how this progresses more towards the final product and finished state. Of course you can have an advanced look at the completed hot rod frame / chassis for my 1929 Ford Roadster. Just go the “PAGES” section new the top right of the screen and click on “Preview of the 1929 Ford Chassis with C4 Corvette suspension.

This frame / chassis will work for any Model A Ford from 1928 to 1931.

I am currently working on CAD drawings for this entire chassis complete with template drawings for all brackets. This will be available soon on this WEB site.

Now it came time to work on what I thought was the most difficult part of the chassis, the front suspension. For the first attempt at this I decided to use exactly the same wheel base as the stock Model A Ford from 1928 to 1931. The front of the frame rails already had the same shape as the stock frame. The only difference was that my frame rails were made of 2” x 4” x 0.1” rectangular tubing. This would make a much more robust frame or chassis. You have to remember the original Model A Ford from 1928 to 1931 did not have much horsepower. I will be using a stock 1986 Corvette engine with over 200hp and over 200 ft-lbs of torque. This is a very important consideration in the hot rod frame or chassis design. The stock Model A Ford from 1928 to 1931 also had all of the cross members riveted to the side of “C” channel frame / chassis rails. Over 70 years these rivets loosen and the general strength of the frame / chassis will be compromised. The frame / chassis I will be designing will not used rivets or “C” channel side rails. All of the required cross members will be welded to the rectangle 2” x 4” x 0.1” rectangular side frame / chassis rails. Just pick up an original Model A Ford from 1928 to 1931 and watch it flex. The hot rod frame / chassis I am designing, using the C4 Corvette suspension components will not have the same flexing issues.

C4 Corvette front cross member stripped down and ready to have measurements taken from. The new street rod cross member will not look anything like this.

I needed to measure everything you could possibly imagine on the C4 Corvette front suspension cross member. The cross memeber comes out of the Corvette as a complete unit. In my case, it was removed from a 1986 Corvette Indy Pace car convertible. I am sure that the Corvette engineers never dreamed of seeing their cars put to this use. Corvette suspensions used in hot rods and custom cars.

The obvious starting point would be to measure the width of the C4 Corvette front cross member at the point where the upper control arms are attached. This measurement was slightly wider than the stock Model A Ford frame / chassis from 1928 to 1931 at the front wheel base center line. I thought that I would mount the controls arms in a similar fashion as the stock C4 Corvette did. It seemed reasonable to make brackets that would mount to the outside edge of the new frame or chassis rails. This meant making the frame slightly wider. In order to make sure this would not create a problem or look terrible when the body was mounted onto the frame, I widen the front frame and quickly lifted the body on to the frame. At that point I realize this would all work out perfectly.

C4 Corvette front suspension mock up for a 1928 to 1931 Model A Ford hot rod chassis / frame. View # 2. An old Jaguar rear end coil over shock was place to visualize possible mounting schemes.

Now I needed to establish the front ride height. Having the entire C4 Corvette front cross member dimensions in hand, it came time to mock up the front suspension. Using some 6” x 6” x 0.25” angle iron as temporary front cross member for the lower control arms was created. The width of the lower part of the cross member was matched to the inside mounting width of the lower control arms removed from the C4 Corvette. It was assembled using c-clamps and tack welded in place. A bracket was created for the upper control arms using angle iron. I clamped these brackets to the top the of the frame rails. Now it came time to mount the C4 Corvette front suspension parts onto the frame mock up and see how everything would like. Remember, humans are very visual, and since I am a professor, I realized that most of what we learn or process would be through our eyes. The brain tends to process the visual information much easier and faster. This is why I needed to mount the rims with tires to the suspension and have the body sitting on the frame. I would quickly see how everything would look. I even used an old Jaguar rear coil over shock to visualized possible mounting schemes for it.

The set up for the front suspension is all very temporary, and is only used to evaluate the ride height and overall look on the hot rod frame / chassis.

Come back next week to see how this progresses more towards the final product and finished state. Of course you can have an advanced look at the completed hot rod frame / chassis for my 1929 Ford Roadster. Just go the “PAGES” section new the top right of the screen and click on “Preview of the 1929 Ford Chassis with C4 Corvette suspension.

This frame / chassis will work for any Model A Ford from 1928 to 1931.